The Family Computer Disk System (Japanese: ファミリーコンピュータ ディスクシステム,Hepburn: Famirī Konpyūta Disuku Shisutemu)[1] is a peripheral for Nintendo's Family Computerhome video game console, released only in Japan on February 21, 1986. It uses proprietary floppy disks called "Disk Cards" for data storage.[2] Through its entire production span, 1986 (1986)–2003 (2003), 4.44 million units were sold. Its name is sometimes shortened as the Famicom Disk System (ファミコンディスクシステム,Famikon Disuku Shisutemu) or simply the Disk System (ディスクシステム,Disuku Shisutemu), and abbreviated as the FDS or FCD.

The device is connected to the Famicom deck by plugging a special cartridge known as the RAM Adapter into the system's cartridge port, and attaching that cartridge's cable to the disk drive. The RAM adapter contains 32 kilobytes (KB) of RAM for temporary program storage, 8 KB of RAM for tile and sprite data storage, and an ASIC known as the 2C33. The ASIC acts as a disk controller for the floppy drive, and also includes additional sound hardware featuring a single-cycle wavetable-lookup synthesizer. Finally, embedded in the 2C33 is an 8KB BIOS ROM. The Disk Cards used are double-sided, with a total capacity of 112 KB per disk. Many games span both sides of a disk, requiring the user to switch sides at some point during gameplay. A few games use two full disks, totaling four sides. The Disk System is capable of running on six C-cell batteries or the supplied AC adapter. Batteries usually last five months with daily game play. The inclusion of a battery option is due to the likelihood of a standard set of AC plugs already being occupied by a Famicom and a television.

In 1983, the disks' 112 KB of storage space was quite appealing due to the high cost of cartridge-based solid state storage chips.[3] The rewritable aspect of the disks also opened up new possibilities; games such as The Legend of Zelda, Metroid, and Kid Icarus were released to the FDS with a save feature. Many of these titles were subsequently ported to cartridge format and released for the NES a year or two later, with saving implemented either via password resume or battery-backed memory.

Widespread copyright violation in Japan's predominantly personal-computer-based game rental market inspired corporations to petition the government to ban the rental of all video games in 1984.[4] With games then being available only via full purchase, demand rose for a new and less expensive way to access more games. In 1986, as video gaming had increasingly expanded from computers into the video game console market, Nintendo installed Famicom Disk Writer Kiosks in game stores across Japan. For a rental fee of 500 yen (then about US$3.25) as opposed to the 2,600 yen (then about US$17) cost of new games, these stations allowed users to copy new games to their disks for an unlimited time. Some game releases were exclusive to these kiosks.[further explanation needed] Calling the Disk Writer "one of the coolest things Nintendo ever created", Kotaku says the system's premise still offers modern retail and online stores a potential innovation in game rentals. The service was very popular and remained available until 2003.[2][3][5]

Disk Writer kiosks in select locations were also provisioned as Disk Fax systems. Players could take advantage of the dynamic rewritability of blue floppy disk versions of Disk System games (such as Famicom Grand Prix: F1 Race) in order to achieve and save their high scores at their leisure at home. The player could then bring the disk to a retailer's Disk Fax kiosk, which collated and transmitted the player's scores via facsimile to Nintendo. Players participated in a nationwide leaderboard, with prizes.[3][6]

The Disk System's Disk Cards are somewhat proprietary 71 mm × 76 mm (2.8 × 3 in) 56K-per-side double-sided floppy. These "Disk Cards," as they are officially called, were a slight modification of Mitsumi's "Quick Disk" 89 mm 2.8 in square disk format which is used in a handful of Japanese computers and various synthesizer keyboards, along with a few word processors. Some of the QuickDisk drives even made it into devices in Europe and North America, though they are somewhat rare. Mitsumi already had close relations with Nintendo, as it manufactured the Famicom and NES consoles, and possibly other Nintendo hardware.

Nintendo's flagship mascot brothers Mario and Luigi make an appearance in the FDS's boot firmware. After turning on the system, a "battle" between the two characters begins over the color scheme of the Nintendo sign and screen border, until a disk is inserted into the FDS.

While the Disk System was years ahead of its time in terms of a disk-format game console, the drive and disks both have reliability issues. The drive belt in the drive is a proprietary size, since standard floppy drive belts are too large. Until 2004, Japanese residents were able to send their systems to Nintendo directly for repairs and belt replacements, but Nintendo of America and the PAL regions do not service them as the system was not released in those regions. Due to a flaw in manufacturing, the old belts have a tendency to break, decompose, or occasionally melt.

In an effort to save money on production, Nintendo opted to not use disk shutters (a feature seen on 89 mm (3.5 in) floppy disks) to keep dirt out, instead opting to include wax paper sleeves as with the older 133 mm (5.25 in) disks. The only exception to this were certain games that were specially released on blue disks, which do have shutters.

Error messages produced during disk read operations are unusually simple, to the point where it is difficult to know what the exact problem is. Most in-game error messages during loading are often displayed as "Err. ##", with ## being the designated number for the type of error message; the most common ones are Err. 02 (the Disk System's batteries being low on power or with no batteries put in altogether), Err. 07 (Side A and B reversed when trying to load the disk), and Err. 27 ("Disk trouble", usually involving the disk surface itself, but can also be due to a belt replacement from an inexperienced technician, resulting in the disk drive's head being inaccurately aligned). However, the error messages themselves consist of little explanation (Err. 27, for example, only gives the accompanying message "Disk trouble") and in most cases within gameplay itself, such as Zelda II: The Adventure of Link, the error message is not given at all, with only the number code shown.

Square Co., Ltd. had a branch at one point called Disk Original Group, a software label that published Disk System titles from Japanese PC software companies. The venture was largely a failure and almost pushed a pre-Final Fantasy Square into bankruptcy. Final Fantasy was to be released for the FDS, but a disagreement over Nintendo's copyright policies caused Square to change its position and release the game as a cartridge.[citation needed]

Nintendo held game score contests for certain games that were released on blue-colored disk cards.[3] Some of the prizes to these contests included two gold prize disks, one for the game Golf US course, and one for Golf Japan course (not to be confused with the title simply called Golf). These two gold disks have metal shutters on them, like the aforementioned blue Disk Cards. Nintendo awarded other prizes including a stationery set, and a gold cartridge version of the Punch-Out!! for the Family Computer. In the gold version of Punch-Out!!, the final opponent is Super Macho Man, before Nintendo used Mike Tyson and Mr. Dream instead in later NES versions.[citation needed]

Many years after the FDS was released, the system and its Disk-kun mascot would be recognized by Nintendo and others. In the GameCube video game Super Smash Bros. Melee, switching the language to Japanese (via the options menu) would also result in the trophy gallery's Nintendo Entertainment System and Super NES being replaced with a Family Computer and Super Famicom, respectively. Additionally, Disk-kun could be unlocked as a trophy via accessing all bonus scores.

The background music to the Nintendo GameCube's main console menu is actually the jingle to the FDS boot-up screen slowed down 16 times.[7]

The FDS boot up theme is briefly played in Paper Mario: The Thousand-Year Door when Princess Peach inserts a floppy disk into Sir Grodus's computer during the fifth chapter's interlude.